Back to wow - where to start ?

Hello everyone, yes it's my first post here, I`ve been mostly lurking here, but on topic. I came back to wow from a break (stopped playing a week after MoP release). I have one lvl90 toon, with mostly quest gear, I heard that to get gear you have to do tons of dailies etc. I want to get him geared for raiding but I don't know where to start, also there is legendary quest line, which I don't know how to start. So my request is: where should I start ? and what have I missed ?

What you've missed I don't know quite much since I've quit myself too since 6 months ago. As for your other question, how you can start out is either get crafted blue gear or if your rich then get trinkets and items from AH but craftable blues are cheaper then queue up for dungeons if you have some missing parts. Do the new Isle of thunder and unlock a 522 neck and a 476 belt (they require some farming but are quite fast to do) also do a scenario I forgot what it was and you'll be awarded with 500+ ilvl boots. Might aswell do the new 5.3 questline and get gear and then your good to queue for your first LFR as by that time you'll have 460+ ilvl. Farm LFR, alongside do dailies (but they're no longer so mandatory and time consuming when MoP came out so it will be quick especially with the new features such as representing a faction in a dungeon or scenario which increases rep) and then your pretty much good to go.

For the legendary, you get a mysterious letter which will direct you to a guy named "Wrathion" and from there you'll begin.

On a side note; forgot scenarios. Scenarios are an even easier way to get geared up but you have to be lucky with RNG as they reward with a satchel-like item which you open it and get 460+ ilvl gear inside.

Convert JP to honor and buy the 476 honor pieces. PvP stats do not factor into the stat budget. From there, do LFR's to gear up and do some of the Isle of Thunder dailies to get runes for the Throne of Thunder LFR.

The legendary quest can be picked up by going to the Tavern in the Mists or by picking up the breadcrumb quest in the Shrine or Shado-Pan Garrison.

I just recently dinged a couple of characters so here's what I do with a fresh 90 with crap gear:

1.) Do world bosses!!! You don't even need to be in the raid group. Just run up to one that's being attacked by your faction and hit it once to get a loot tag. Galleon and Ooondasta have long respawn timers, but Nalak and Sha are quick respawn and usually early in a reset there's be lots of groups going. Yesterday, reset day, Nalak was being killed pretty much within 10 min of each respawn. All of my alts usually have multiple pieces of epic gear before they even hit 90 because I make sure to run them to world bosses while leveling.

2.) Go to Isle of Thunder. When you first get there, there's a series of solo scenarios. Some of those might be a little rough with bad gear and you'll probably die a few times. I recommend going through the whole series to unlock the whole island, but that's not needed right away. What you do want to get right away is a key. And you get keys by killing the rares that spawn on the island. Usually in general chat there'll be a few call outs when rares spawn. If there are a few people grouping for it, join the group so you can see where you should go. If not, you can hang out around some easy to reach rares like Goda and Al. You'll almost always get the key drop on your first or second rare kill of the week.

3.) Trove scenario. Once you get the key, go to where the quartermaster is inside the cave to the left of the bottom of the stairs. You get a quest to find someone in that cave when you first go to the island so it should be easy to find. A female Pandaren standing at the table will give you an option to run the Trove of the Thunder King scenario. Run around the first room killing all spiders and looting every chest you can. You can get a good amount of Greater Coins this way that you can spend in LFR or on the older world bosses.

4.) Do Battlefield Barrens questline. One of the quests gives you ilvl 502 boots plus you want to do the weekly as much as possible. Doing the weekly gives you some lesser coins as well as gives you pretty much a piece of ilvl 489 gear every week.

Once you get your ilvl above 460, start running LFR. More LFR open up at ilvl 470 and 480. Just remember to do world bosses, battlefield barrens, and trove scenario each week and you'll be geared out in no time!